1. Field of the Invention
This invention relates to surfactants, emulsifiers for use in emulsion polymerization, dispersants for use in suspension polymerization and modifiers for use in modification of resin properties, with each of these four agents comprised of a compound having a dibasic carboxyl group in its configuration.
2. Description of the Related Art
For their diversified properties such as emulsification, dispersion, cleaning, wetting, frothing and the like, surfactants have heretofore found applications in a wide variety of industrial sectors including textiles, paper, rubber, plastics, metals, paints, pigments, civil engineering, construction and the like. In recent years, moves toward more sophisticated end products using surfactants are becoming particularly active. Along with this, certain secondary defects of surfactants have been recognized.
For instance, such surfactants are absolutely necessary for paint, printing ink and adhesives when these agent products are manufactured, when they are stabilized, or when they are applied. No surfactants need be incorporated in these agents where they are applied by means of coating, printing, adhering or tacking. Conversely, if a surfactant is present in these agents, it is in most instances liable to impair the water resistant and oil resistant properties of the resulting coat, printed surface or adhesive film.
To cope with these problems, attempts have been made to reduce the amount of surfactant to be used and to render it highly polymeric, but only less than satisfactory results have been achieved with respect to the stability and workability properties of the finished product.
Also as emulsifiers for emulsion polymerization, there have been employed anionic surfactants such as alkylsulfuric acid salts, alkylbenzene sulfuric acid salts, polyoxyethylene alkylether sulfuric acid salts an d the like, and nonionic surfactants such as polyoxyethylene alkylethers, polyoxyethylene aliphatic acid esters, Pluronic type surfactants and the like.
As is generally known in the art, an emulsifier for emulsion polymerization takes part not only in the initiation and propagation of polymerization, but also in the mechanical stability, chemical stability, freeze stability and storage stability of the resultant emulsion. Furthermore, the emulsifier has a great effect upon the physical properties of the emulsion such as particle size, viscosity and frothing and upon the physical properties of a film resulting from the emulsion polymer such as water resistance, weathering resistance, adhering bond and thermal stability.
Conventional emulsifiers, however, are responsible for formation of an emulsion that has excessive frothing brought on by the emulsifier and moreover for formation of a film from the emulsion polymer that is poor in adhesiveness and in resistance to water, weather and heat due to the emulsifier remaining in a free state in the film.
In order to eliminate the above-mentioned drawbacks of the emulsifiers in common use, it has recently been developed a reactive surfactant which has an emulsifiable group and a polymerizable group and acts not only as an emulsifier, but also as a surfactant which gradually chemically bonds to a polymer having been formed while in polymerization. For example, Japanese Patent Laid-Open Nos. 7-10909 and 7-18009 are cited on this point. These prior publications disclose carboxylation using chloracetic acid or its salt. Such known reactions lead to reduced reactivity and to increased by-product. Hence, the problems noted hereinabove in connection with the conventional emulsifiers are left unsolved without any significant countermeasures being found.
Dispersants are used for suspension polymerization of vinyl monomers. This mode of polymerization has been widely carried out commercially by dispersing a vinyl monomer in an aqueous medium and subsequently by causing the resultant dispersion to suspension-polymerize in the presence of an oil-soluble catalyst.
The qualities of the polymer products thus obtained are dominated by various polymerizing factors such as polymerization rates, water to monomer ratios, polymerization temperatures, kinds and amounts of catalysts, types of reactors, stirring speeds, and kinds and amounts of dispersants. In particular, the kind of a dispersant to be used, among these factors, is known to have a strong effect upon the polymer qualities.
Dispersants commonly accepted for suspension-polymerizing vinyl monomers include cellulosic derivatives such as methyl cellulose, hydroxypropylmethyl cellulose, carboxyl methyl cellulose and the like, and water-soluble polymers such as gelatin, polyvinyl alcohol and the like.
However, the above listed dispersants tend to remain in free condition in the finished vinyl resins, hence reducing the physical resin properties with respect to water and weather resistance and durability.
On the other hand, a certain modifier for modifying the properties of vinyl resins is known as disclosed in Japanese Patent Laid-Open No. 1-174511. Being less compatible with a monomeric vinyl, this prior art modifier fails to produce a homogeneous copolymer.
As taught by Japanese Patent Laid-Open No. 1-174512, it has also been proposed to improve the compatibility of a resin modifier with a vinyl monomer. However, the modifier described here is not sufficiently compatible with the monomer with less effective modification of the resulting polymer.